The aim of this project is to develop an efficient procedure in which we can investigate the interaction between cytokines and their receptor subunits, between receptor subunits mutually, and of the induced components of an active receptor complex. Therefore, functional chemeric receptor complexes were developed, in which the extracellular parts of the interferon type I receptor are replaced by the extracellular parts of other cytokine receptors. Another goal of this project is to characterize the precise role of the IFNaR1 and the IFNa2-2 chain in the signaling process. Finally, a procedure for the identification of the ligands of so-called 'orphan receptors' will be developed.